The present invention relates to coupling mechanisms for coupling power tools to tool bits and, more specifically, relates to the coupling of bits, such as chisel bits, for pneumatic impact tools.
Heretofore, power impact tools, such as air hammers and the like, have typically been provided with quick-coupling mechanisms for mounting tool bits. One common quick-coupling arrangement includes a coupler with spring-biased balls which project radially into a bit shank-receiving bore and engage a raised shoulder or flange on the bit shank. Upon insertion of the bit, the shoulder or flange snaps past the balls, which then cooperate with the flange to resiliently retain the bit in place. Such couplers rely on the spring-biased balls to provide the retention, the balls affording only line contact with the bit shoulder. Bits may inadvertently become disengaged from such couplers in use. Furthermore, the coupler mechanism is typically adapted to be mounted on the front end of the tool, substantially extending the overall length of the tool.
It is known in other types of tools to provide a quick-coupling of bits and the like by use of a keyed coupler with a keyway for receiving a key portion of the bit shank which, once inserted, is rotated to move the key out of alignment with the keyway to retain the bit in place. However, such rotatably latching coupling mechanisms have heretofore been provided with very specialized, and sometimes complicated designs.